Cycling in the heat

Gosh. 

The setup:
My husband's brother is supposed to come tomorrow as they have planned to cycle 140km or so.

So I assume I will not cycle tomorrow and as I cycled even less during last week when my husband was away, today was the only cycling day for me if I wanted to do any longer route,

We left fairly early, but it was 27 already and very quickly it rose to 29 and even to 30°C. Our route was 31,2km (my choice) but towards the end I discovered that I'm not strong enough to do that distance in that heat. I managed to come home, but it nearly wiped me out. Note to self. Not that long routes in that kind of heat.